Table 2. Quality assessment for the studies included in the meta-analysis.

Study	Randomization process	Estimation of sample size	Allocation concealment	Intention to treat analysis	Dropout	Jadad score
Pierre et al. 1999 [5]	Yes	Yes	No	Yes	Yes	3
Zhi et al. 2004 [21]	Yes	Yes	No	Yes	Yes	3
Ren et al. 2004 [25]	Yes	Yes	No	No	No	2
Su et al. 2006 [22]	Yes	Yes	No	No	No	2
Wang et al. 2008 [26]	Unclear	Yes	No	No	No	1
Liang et al. 2011 [27]	Unclear	Yes	No	No	No	1
Luo et al. 2012 [30]	Unclear	Yes	No	No	No	1
Xie et al. 2013 [28]	Yes	Yes	No	No	No	2
Lo-Coco et al. 2013 [12]	Yes	Yes	Yes	Yes	Yes	3
Zhu et al. 2013 [14]	Yes	Yes	No	Yes	No	3
Li et al. 2014 [23]	Unclear	Yes	No	No	No	1
Liu et al. 2014 [29]	Yes	Yes	No	No	No	2
Li et al. 2015 [24]	Unclear	Yes	No	No	No	1
Alan et al. 2015 [13]	Yes	Yes	Yes	Yes	Yes	3